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AIXpert Blog

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AIXpert Blog is about the AIX operating system from IBM running on POWER based machines called Power Systems and software related to it like PowerVM for virtualisation, PowerVC for Deploying VM's and PowerSC for security plus performance monitoring and nmon

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So you know about Power7 Local, Near and Far memory for your actual machine but what is your Virtual Machine (LPAR) actually using? There are three key commands to show you (lssrad, mpstat and topas) and we will look at some example output. First, we need to define an SRAD or a Scheduler Resource Affinity Domain . If you have used Resource Sets with AIX WLM or WPAR then you have a good idea what these are like. An SRAD is a group of resources but in our case CPU/cores and the associated memory that is directly attached to it. As an... [More]

I need you to help me settle an argument or rather lack of information. I am getting conflicting messages about whether these smaller Power7 machines use Local and Near or Local and Far memory. I documented what I thought was correct in the Part 1 of this series of blog's. Actually, there is not much difference as these machines have two tiers of memory like "on the chip" or "some where else" so the names are hardly vital but I would like my facts straight. Unfortunately, I don't have examples of these machines with more... [More]

Finally, I have the types of memory by POWER7 model double checked. I refreshed the table in part 1 but thought I should make sure every one sees the final version so I have not mislead people. Only the Power 770/780 and Power 797 have Near memory. All the smaller machine operate a Local memory meaning on the same same POWER7 chip and Far memory for any access to another POWER7 chip's memory.

I just realised that I got help from the AIX developers to explain the output of the mpstat -d command for my POWER7 and Affinity Technical University sessions in Miami and Copenhagen that I never passed on to every one. In an earlier blog we examined some mpstat columns but skipped others. The nearly undocumented mpstat stats are: S0rd, S1rd, S2rd, S3rd, S4rdand S5rd. In the AIX manuals it states: S0rd = The percentage of thread re-dispatches
within the scheduling affinity domain 0.
And likewise for the other numbers - but what does... [More]

Time to correct a few assumptions and statements that I made a while back. Previously I said the POWER Hypervisor decides where to put a Virtual Machine (VM/LPAR) based on the Virtual Processor number (spreading factor). Well, apart from it nearly being right ... I was actually wrong! I got talking to one of these very impressive Hypervisor developers in Germany and he put me right. In most of my larger machines, I do what I think is fairly normal for creating an VM - like working with a CPU core to RAM ratio that my customers use, like 1... [More]